Color filter array and method of fabrication and use

ABSTRACT

A pixel cell with a photosensitive region formed in association with a substrate, a color filter formed over the photosensitive region, the color filter comprising a first material layer and a second material layer formed in association with the first shaping material layer.

FIELD OF THE INVENTION

Embodiments of the invention relate generally to semiconductor devicesand in particular to imager devices and methods of forming and using thesame.

BACKGROUND OF THE INVENTION

Imager devices, including charge coupled devices (CCD), complementarymetal oxide semiconductor (CMOS) sensors, and others have commonly beenused in photo-imaging applications. A CMOS imager circuit includes afocal plane array of pixel cells, each one of the cells including aphotosensitive region (or photosensor), for example, a photogate,photoconductor or a photodiode for accumulating photo-generated chargein the specified portion of the substrate. Each pixel cell has a chargestorage region, formed on or in the substrate, which is connected to thegate of an output transistor that is part of a readout circuit. Thecharge storage region may be constructed as a floating diffusion region.In some imager circuits, each pixel may include at least one electronicdevice such as a transistor for transferring charge from the photosensorto the storage region and one device, also typically a transistor, forresetting the storage region to a predetermined charge level prior tocharge transference.

In a CMOS imager, the active elements of a pixel cell perform thefunctions of: (1) photon to charge conversion; (2) accumulation of imagecharge; (3) resetting the storage region to a known state; (4) transferof charge to the storage region; (5) selection of a pixel for readout;and (6) output and amplification of signals representing pixel resetlevel and pixel charge. Photo charge may be amplified when it moves fromthe initial charge accumulation region to the storage region. The chargeat the storage region is typically converted to a pixel output voltageby a source follower output transistor.

Examples of CMOS imaging circuits, processing steps thereof, anddetailed descriptions of the functions of various CMOS elements of animaging circuit are described, for example, in U.S. Pat. No. 6,140,630;U.S. Pat. No. 6,376,868; U.S. Pat. No. 6,310,366; U.S. Pat. No.6,326,652; U.S. Pat. No. 6,204,524; U.S. Pat. No. 6,333,205; and U.S.Pat. No. 6,852,591, all of which are assigned to Micron Technology, Inc.The disclosures of each of the foregoing are hereby incorporated byreference in their entirety.

The use of microlenses significantly improves the photosensitivity ofthe imaging device by collecting light from a large light collectingarea and focusing it onto a small photosensitive area of thephotosensor. Each photosensor is typically fabricated to absorb awavelength of light associated for a particular color. Color filterarrays, typically formed below the microlenses, have been used to filterwavelengths of light associated with particular colors that are notintended to strike the underlying photosensor. Conventional color filterarrays are patterned and reflowed over respective photosensors.Microlens precursor blocks are subsequently patterned on the colorfilter array, and reflowed to produce a hemi-spherical shape to theoverall microlens. During reflow of the color filter array, however, thepatterned structures typically contract resulting in an uneven surfaceon which the microlens precursor blocks are formed. Contraction of up to10% of the materials used to form the color filters is not uncommon.Microlenses subsequently formed over the contracted and uneven colorfilter array may have uncontrollably shifted focal points relative to acenter of underlying photosensors.

The uncontrollably shifted focal points of the microlenses may result inincreased cross-talk or a reduced efficiency of light capture.“Cross-talk” results when off-axis wavelengths of light strike amicrolens or color filter at an obtuse angle of incidence. The off-axiswavelengths of light pass through material layers and miss the intendedphotosensors, and instead strike adjacent photosensors. Reduced lightconversion efficiency may occur when the off-axis wavelengths strike aless than optimal spot on an intended photosensor. The problem ofcontracted color filter arrays is exacerbated by asymmetrical pixel cellarchitectures that have recently been proposed to increase photosensorarray density. Asymmetrical pixel cell architecture demands the preciseplacement of color filters and overlying microlenses to focus light ontothe photosensor. The slightest contraction of the color filter array andoverlying microlenses may have detrimental effects upon the incidence ofcross-talk.

Additionally, spaces or gaps between the color filters in the array maycause subsequently formed microlens precursors to assume a “bowed” oruneven topmost surface. Once the microlens precursors are patterned andreflowed, the microlenses shift, relative to a center of the underlyingphotosensor, into the bowed area, which may also result in increasedcross-talk.

Accordingly, it is desirable to form color filter arrays having asubstantially gapless surface for overlying microlenses formed thereon.By reducing the gapping between color filters in the color filter array,an overlying microlens array may have a reduced number of microlenseswith shifted focal points. Additionally, due to the inevitability ofshifting microlenses, it is desirable to control the shifting bycontrolling the shapes of the underlying color filters.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C illustrate top-down and partial cross-sectional views of animager device constructed in accordance with an embodiment of theinvention;

FIGS. 2A-2D illustrate a method of fabricating the imager deviceillustrated in FIGS. 1A-1B;

FIG. 3 illustrates a partial cross-sectional view of an imager deviceconstructed in accordance with a second embodiment of the invention

FIG. 4 illustrates a partial cross-sectional view of an imager deviceconstructed in accordance with a third embodiment of the invention;

FIGS. 5A-5B illustrate partial top-down and cross-sectional views of animager device constructed in accordance with a fourth embodiment of theinvention;

FIG. 6 illustrates a partial cross-sectional view of an imager deviceconstructed in accordance with a fifth embodiment of the invention;

FIG. 7 illustrates a partial cross-sectional view of an imager deviceconstructed in accordance with a sixth embodiment of the invention;

FIG. 8 illustrates a partial cross-sectional view of an imager deviceconstructed in accordance with a seventh embodiment of the invention;

FIGS. 9A-9B illustrate partial top-down and partial cross-sectionalviews, respectively, of an imager device constructed in accordance witha eighth embodiment of the invention;

FIGS. 10A-10B illustrates a partial cross-sectional view of an imagerdevice constructed in accordance with a ninth embodiment of theinvention;

FIG. 11 is a block diagram of a device incorporating the imager deviceconstructed in accordance with FIGS. 1A-1B; and

FIG. 12 is a block diagram of a processor system incorporating the FIG.11 imaging device in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, reference is made to variousspecific embodiments of the invention. These embodiments are describedwith sufficient detail to enable those skilled in the art to practicethe invention. It is to be understood that other embodiments may beemployed, and that various structural, logical and electrical changesmay be made. The term “substrate” used in the following description mayinclude any supporting structure including, but not limited to, asemiconductor substrate that has an upper semiconductor substratesurface. A semiconductor substrate should be understood to includesilicon, silicon-on-insulator (SOI), silicon-on-sapphire (SOS), dopedand undoped semiconductors, epitaxial layers of silicon supported by abase semiconductor foundation, and other semiconductor structures,including those made of semiconductors other than silicon. Whenreference is made to a semiconductor substrate or wafer in the followingdescription, previous process steps may have been utilized to formregions or junctions in or over the base semiconductor or foundation.The substrate also need not be semiconductor-based, but may be anysupport structure suitable for supporting an integrated circuit,including, but not limited to, metals, alloys, glasses, polymers,ceramics, and any other supportive materials as is known in the art.

The term “pixel cell,” as used herein, refers to a photo-element unitcell containing a photosensitive region for converting photons to anelectrical signal as may be employed by an imager device. Although thepixel cells are illustrated herein as CMOS four-transistor (or 4-T)pixel cells for convenience of description, the embodiment of theinvention is not limited to any particular solid state sensor or anyparticular pixel cell architecture. For example, the pixel cells couldhave more or less than four transistors and the invention may beemployed in any type of solid state imager device, CCD sensors being butone example.

With reference to the figures, where like numerals represent likeelements, FIGS. 1A, 1B and 1C, respectively illustrate a partialtop-down view, a partial cross-sectional view along the lines I-I ofFIG. 1A, and a partial cross-sectional view along the lines II-II ofFIG. 1A of a semiconductor-based imager device 100, such as a CMOSimager, constructed in accordance with an embodiment of the invention.The imager device 100 includes a pixel cell array 101 with first,second, and third pixel cells 102 _(B), 102 _(G), 102 _(R),respectively. First, second, and third pixel cells 102 _(B), 102 _(G),102 _(R) correspond to wavelengths of light associated with the colorsblue, green, and red, respectively. Those of ordinary skill in the artwill recognize that the illustrated example is not intended to belimiting, and that first, second, and third pixel cells 102 _(B), 102_(G), 102 _(R) could correspond to wavelengths of light associated withother colors of light; for example, cyan, magenta, and yellow and theremay be more or less than there color pixels. It should also be notedthat although FIGS. 1A, 1B, and IC illustrate several pixel cells in thepixel cell array 101, the pixel cell array 101 could contain millions ofpixel cells.

FIG. 1A illustrates first, second, and third pixel cells 102 _(B), 102_(G), 102 _(R) having respective first, second, and third photosensitiveregions 104 _(B), 104 _(G), 104 _(R) fabricated on a semiconductorsubstrate 106. The first, second, and third pixel cells 102 _(B), 102_(G), 102 _(R) also include respective first, second, and third colorfilters 108 _(B), 108 _(G), 108 _(R) formed at a higher level of theillustrated pixel cell structure over respective first, second, andthird photosensitive regions 104 _(B), 104 _(G), 104 _(R) and over apassivation layer 120. The first, second, and third color filters 108_(B), 108 _(G), 108 _(R) comprise respective first, second, and basematerial layers 181 _(B), 181 _(G), 181 _(R) formed in association withrespective first, second, and third conforming layers 182 _(B), 182_(G), 182 _(R) and over the passivation layer 120. The pixel cell arrayalso includes respective first, second, third microlenses 103 _(B), 103_(G), 103 _(R) formed over the color filters 108 _(B), 108 _(G), 108_(R).

As illustrated in FIG. 1B, the pixel cell array 101 also includes alight shield 126 having openings 126 a in optical alignment withrespective photosensitive regions 104 _(B), 104 _(G), 104 _(R), andother conventional layers illustrated as first, second, and thirdinterlayer dielectrics 172, 174, 176, respectively, and an insulatinglayer 170 over the active electrical elements of the pixel cells 102_(B), 102 _(G), 102 _(R).

FIG. 1C illustrates a partial cross-sectional view taken along threesecond pixel cells 102 _(B). The second color filters 108 _(B) arecoextensive with one another (also illustrated in FIG. 1A). The secondconforming layers 182 _(B) of each of the second color filters 108 _(B)are substantially gapless, and collect more light than if the secondconforming layers 182 _(B) of each of the second color filters 108 _(B)were not coextensive.

The imager device 100 of FIGS. 1A, 1B, and 1C has color filters (e.g.,first, second, and third color filters 108 _(B), 108 _(G), 108 _(R))that are not contracted relative to a center of the underlyingphotosensors (e.g., first, second, and third photosensors 104 _(B), 104_(G), 104 _(R)), and have microlenses (e.g., first, second, and thirdmicrolenses 103 _(B), 103 _(G), 103 _(R)) which are in optical alignmentwith respective photosensitive regions 104 _(B), 104 _(G), 104 _(R). Theformation of the conforming layers (e.g., first, second, and thirdconforming layers 182 _(B), 182 _(G), 182 _(R)) over the base materiallayers (e.g., first, second, and third base material layers 181 _(B),181 _(G), 181 _(R)) may provide a substantially more planar first,second, and third color filters 108 _(B), 108 _(G), 108 _(R) formed overthe semiconductor substrate 106 that conventional processes, discussedabove with respect to the Background. Moreover, the microlenses formedthereon (e.g., first, second, and third microlenses 103 _(B), 103 _(G),103 _(R)) may have reduced shifted focal points relative to a center ofthe underlying photosensitive regions 104 _(B), 104 _(G), 104 _(R). As aresult, the imager device 100 may have a substantially reduced amount ofcross-talk between pixel cells.

The first, second, and third color filters 108 _(B), 108 _(G), 108 _(R)correspond to a filter allowing first, second, and third wavelengths oflight to strike respective photosensitive regions 104 _(B), 104 _(G),104 _(R). Each of the microlenses 103 _(B), 103 _(G), 103 _(R) has arespective radius of curvatures R_(B), R_(G), R_(R) (FIG. 1B) that maybe optimized to direct light of a particular wavelength to differentdepths within the photosensitive regions.

Additionally, the refractive indexes of the base material layers 181_(B), 181 _(G), 181 _(R) and the conforming layers 182 _(B), 182 _(G),182 _(R) are different, but need not be so. For example, the first basematerial layers 181 _(B), 181 _(G), 181 _(R) and the conforming layers182 _(B), 182 _(G), 182 _(R) could be different from one another, andselected such that the refractive indexes focus light of a particularwavelength onto the focal plane 122 of the photosensitive regions 104_(B), 104 _(G), 104 _(R). The illustrated base material layers 181 _(B),181 _(G), 181 _(R) are greater than the conforming layers 182 _(B), 182_(G), 182 _(R).

The imager device 100 of FIGS. 1A-1C has color filters that arefabricated in a manner as to decrease the susceptibility of contractionof the color filter array 111, as discussed in greater detail below. Thedecrease in the contraction of the color filter array 111 results indecreased cross-talk which may be associated with conventional methodsof fabricating color filter arrays.

As discussed above with respect to FIG. 1C, adjacent second colorfilters 108 _(G) can be fabricated to be coextensive, reducing theamount of gapping between adjacent color filters. The reduction ingapping improves the amount of light capture, and also decreases theamount of possible cross-talk, or undirected light striking thephotosensitive region array 112.

FIGS. 2A-2D illustrate a method of fabricating the FIG. 1B imager device100 taken along line I-I of FIG. 1A. Specifically, FIG. 2A illustratesthe patterning of the first, second, and third base material layers 181_(B), 181 _(G), 181 _(R) over the passivation layer 120 of the imagerdevice 100. The first, second, and third base material layers 181 _(B),181 _(G), 181 _(R) could be formed of any transparent materialincluding, but not limited to, zinc selenide (ZnSe), silicon oxide,silicon nitride, silicon oxynitride, silicon-carbon (SiC) (BLOk),tantalum pentoxide (Ta₂O₅), titanium oxide (TiO₂),polymethylmethacrylate, polycarbonate, polyolefin, cellulose acetatebutyrate, polystyrene, polyimide, epoxy resin, photosensitive gelatin,acrylate, methacrylate, urethane acrylate, epoxy acrylate, polyesteracrylate, or a positive or negative photoresist such as a 3000 seriesphotoresist material (or any other series of photoresist material)produced by FUJIFILM Electronic Materials (FFEM), Japan, including, butnot limited to color resists known in the art as SB-3000L, SG-3000L andSR-3000L for blue, green, and red color filters, respectively. It shouldalso be noted that the materials could be selected from a manufacturerother than FUJIFILM, and that the materials could be any color filteringmaterial.

The materials selected should correspond to filtering a particularwavelength of light from striking the photosensitive regions 104 _(B),104 _(G), 104 _(R). Accordingly, in one embodiment of the invention, thefirst, second, and third base material layers 181 _(B), 181 _(G), 181_(R) comprise SB-3000L, SG-3000L and SR-3000L, respectively. The basematerial layers 181 _(B), 181 _(G), 181 _(R) are deposited over thepassivation layer 120 by conventional coating methods, including, butnot limited to, spin-coating methods, and selectively patterned over thefirst, second, and third photosensitive regions 104 _(B), 104 _(G), 104_(R), respectively.

The base material materials 181 _(B), 181 _(G), 181 _(R) can beselectively patterned by forming base material layer precursors over thephotosensitive regions 104 _(B), 104 _(G), 104 _(R), and selectivelyexposing the base material layer precursors to ultraviolet (UV) light.As known in the art, a negative photoresist is polymerized when exposedto UV light. Accordingly, if negative photoresist materials are used toform the first, second, and third base material layers 181 _(B), 181_(G), 181 _(R) the base material layer precursors are selectively maskedsuch that only those portions of the base material layer precursorsintended to form first, second, and third base material layers 181 _(B),181 _(G), 181 _(R) are exposed to UV light. Those portions that areunnecessary are not exposed to light, and are removed by a developersolution.

Conversely, a positive photoresist is exposed with UV light wherever theunderlying material is to be removed. Accordingly, if positivephotoresist materials are used to form first, second, and third basematerial layers 181 _(B), 181 _(G), 181 _(R), the base material layerprecursors are selectively masked such that only those portions of thebase material layer precursors that are unnecessary are exposed tolight, and are subsequently removed by a developer solution. Theunexposed portions of the positive photoresist remain behind to form thefirst, second, and third base material layers 181 _(B), 181 _(G), 181_(R).

It should be noted that although FIG. 2A illustrates the deposition andpatterning of the first, second, and third base material layers 181_(B), 181 _(G), 181 _(R) in a single step, one of ordinary skill in theart will recognize that the base material layers 181 _(B), 181 _(G), 181_(R) are layered over the passivation layer 120 in separate steps. Forexample, the precursor to the first base material layer 181 _(B) couldbe deposited by conventional coating methods, including, but not limitedto, spin-coating methods, over the passivation layer 120, masked,exposed to UV light, and exposed to developer to pattern the first basematerial layers 181 _(B). A precursor to the second base material layer181 _(G) can subsequently be deposited over the passivation layer 120,masked, exposed to UV light, and exposed to developer to pattern thesecond base material layers 181 _(G). Lastly, a precursor to the thirdbase material layer 181 _(R) can be deposited over the passivation layer120, masked, exposed to UV light, and exposed to developer to patternthe third base material layers 181 _(R).

Additionally, it should be recognized that the first, second, and thirdbase material layers 181 _(B), 181 _(G), 181 _(R) could all be formed ofa material that does not filter any particular wavelength of lightassociated with a particular color. For example, the first, second, andthird base material layers 181 _(B), 181 _(G), 181 _(R) could all beformed of a clear, transparent material, simplifying the processingsteps involved in making the first, second, and third base materiallayers 181 _(B), 181 _(G), 181 _(R) by patterning a single material forall three base material layers.

As illustrated in FIG. 2A, the first, second, and third base materiallayers 181 _(B), 181 _(G), 181 _(R) contract from their original sizeduring processing, as illustrated by the dashed lines, and discussedabove with respect to the Background. Contraction of approximately 10%of the width may occur. Therefore, a base material layer formed over thepassivation layer 120 that is 10 microns wide (as measured by a sidecross-sectional view) could contract as much as 1 micron (or, asillustrated, 0.5 microns on both sides of the first, second, and thirdbase material layers 181 _(B), 181 _(G), 181 _(R)), leaving a gapbetween the base material layers (e.g., first and second base materiallayers 181 _(B), 181 _(G)) of approximately 1 micron.

FIG. 2B illustrates the deposition of the first conforming layer 182_(B). The first conforming layer 182 _(B) could be formed of anytransparent material including, but not limited to, zinc selenide(ZnSe), silicon oxide, silicon nitride, silicon oxynitride,silicon-carbon (SiC) (BLOk), tantalum pentoxide (Ta2O5), titanium oxide(TiO2), polymethylmethacrylate, polycarbonate, polyolefin, celluloseacetate butyrate, polystyrene, polyimide, epoxy resin, photosensitivegelatin, acrylate, methacrylate, urethane acrylate, epoxy acrylate,polyester acrylate, or a positive or negative photoresist such as amaterial consisting of a 3000 series material fabricated by FUJIFILMElectronic Materials (FFEM), Japan, including, but not limited to colorresists such as SB-3000L, SG-3000L and SR-3000L for blue, green, and redcolor filters, respectively. The illustrated first conforming layer 182_(B) is formed of SB-3000L, the same material used for the underlyingbase material layer 181 _(B).

The illustrated first conforming layer 182 _(B) is deposited byconventional methods, including, but not limited to, spin-coatingmethods. The spin-coating technique provides a simplified fabricationprocess resulting in a material layer with minimal fabricating costs.During the deposition of the first conforming layer 182 _(B), theunderlying first base material layer 181 _(B) acts as a barrier overwhich the material forming the first conforming layer 182 _(B) musttraverse. The first conforming layer 182 _(B) conforms to the contoursof the uneven surface of the intermediate structure, and flows into thegaps or spaces between the base material layers.

As discussed below, the first conforming layer 182 _(B) may haveinherent surface tensions that are selected to provide different shapesto any of the first, second, and third conforming layers 182 _(B), 182_(G), 182 _(R). Different materials have different inherent surfacetension properties (measured in dynes/cm); accordingly, the materialforming the first conforming layer 182 _(B) could be selected for theintended application. For example, a material having a higher surfacetension is used for applications in which a more spherical shape thanillustrated in FIG. 2B is desired. Conversely, a material having a lowersurface tension is used for applications in which a substantially planarsurface is desired. The surface tension of the illustrated firstconforming layer 182 _(B) is low, thereby creating a substantiallyplanar surface.

It should be noted, however, that materials often have varying degreesof surface tension depending on the conditions in which the materialsare deposited. For example, materials typically have a greater surfacetension at cooler temperatures (e.g., 20° C.) as compared to the surfacetension of the material at higher temperatures (e.g., 70° C.).Therefore, the conditions at which the first conforming layer 182 _(B)is deposited can be varied to shape the resulting first color filter 108_(B) (FIG. 1B).

FIG. 2B also illustrates a mask 190 formed over portions of the firstconforming layer 182 _(B)′, which is formed of a negative photoresist.The entire FIG. 2B structure is then exposed to UV light to polymerizethe exposed first conforming layer 182 _(B). The mask 190 is removed,and the portions of the first conforming layer 182 _(B)′ that were notpolymerized are dissolved by a developer solution, leaving behind onlythe first conforming layer 182 _(B) over the first photosensitive region104 _(B). As illustrated, the first, second, and third base materiallayers 181 _(B), 181 _(G), 181 _(R) are substantially immune fromfurther contraction; as illustrated in FIG. 2C, however, the firstconforming layer 182 _(B) does contract during processing.

FIG. 2C illustrates the deposition of the second conforming layer 182_(G). The second conforming layer 182 _(G) could be formed of anytransparent material including, but not limited to, zinc selenide(ZnSe), silicon oxide, silicon nitride, silicon oxynitride,silicon-carbon (SiC) (BLOk), tantalum pentoxide (Ta₂O₅), titanium oxide(TiO₂), polymethylmethacrylate, polycarbonate, polyolefin, celluloseacetate butyrate, polystyrene, polyimide, epoxy resin, photosensitivegelatin, acrylate, methacrylate, urethane acrylate, epoxy acrylate,polyester acrylate, or a positive or negative photoresist such as amaterial consisting of a 3000 series material fabricated by FUJIFILMElectronic Materials (FFEM), Japan, including, but not limited to colorresists such as SB-3000L, SG-3000L and SR-3000L for blue, green, and redcolor filters, respectively. The illustrated conforming layer 182 _(G)is formed of SG-3000L, the same material used for the underlying basematerial layer 181 _(G).

The illustrated second conforming layer 182 _(G) is deposited byconventional coating methods, including, but not limited to,spin-coating methods, as discussed above with respect to FIG. 2B. Duringthe deposition of the second conforming layer 182 _(G), the underlyingsecond base material layer 181 _(G) acts as a barrier over which thematerial forming the second conforming layer 182 _(G) must traverse, asdiscussed above with respect to FIG. 2B. The second conforming layer 182_(G) fills the gaps between the color filters (e.g., first, second, andthird color filters 108 _(B), 108 _(G), 108 _(R) of FIG. 1B). Like thesecond conforming layer 182 _(B), the second conforming layer 182 _(G)can be selected or deposited in conditions to have a predeterminedsurface tension.

Masks 190 are selectively placed over the first conforming layer 182Band the third base material layer 182 _(R). The entire FIG. 2C structureis subsequently exposed to UV light, which polymerizes the secondconforming layer 182 _(G). The masks 190 are removed, and portions ofthe second conforming layer 182 _(G)′ are subjected to developer andremoved.

FIG. 2D illustrates the deposition of the third conforming layer 182 c.The third conforming layer 182 c could be formed of any transparentmaterial including, but not limited to, zinc selenide (ZnSe), siliconoxide, silicon nitride, silicon oxynitride, silicon-carbon (SiC) (BLOk),tantalum pentoxide (Ta₂O₅), titanium oxide (TiO₂),polymethylmethacrylate, polycarbonate, polyolefin, cellulose acetatebutyrate, polystyrene, polyimide, epoxy resin, photosensitive gelatin,acrylate, methacrylate, urethane acrylate, epoxy acrylate, polyesteracrylate, or a positive or negative photoresist such as a materialconsisting of a 3000 series material fabricated by FUJIFILM ElectronicMaterials (FFEM), Japan, including, but not limited to color resistssuch as SB-3000L, SG-3000L and SR-3000L for blue, green, and red colorfilters, respectively. The illustrated conforming layer 182 _(R) isformed of SR-3000L, the same material used for the underlying basematerial layer 181 _(R).

The illustrated third conforming layer 182 _(R) is deposited byconventional coating methods, including, but not limited to,spin-coating methods, as discussed above with respect to FIG. 2B. Duringthe deposition of the third conforming layer 182 _(R), the underlyingthird base material layer 181 _(R) acts as a barrier over which thematerial forming the third conforming layer 182 _(R) must traverse, asdiscussed above with respect to FIG. 2B. The third conforming layer 182_(R) fills the gaps between the color filters (e.g., first, second, andthird color filters 108 _(B), 108 _(G), 108 _(R) of FIG. 1B). Like thesecond conforming layer 182 _(B), the third conforming layer 182 _(R)can be selected or deposited in conditions to have a predeterminedsurface tension.

A mask 190 is selectively placed over the first and second conforminglayers 182 _(B), 182 _(G). The entire FIG. 2D structure is subsequentlyexposed to UV light, which polymerizes the third conforming layer 182_(R). The mask 190 is removed, and portions of the second conforminglayer 182 _(R)′ are subjected to developer and removed. Microlensprecursor blocks are patterned and reflowed over the microlens array 111(FIG. 1B), resulting in the imager 100 illustrated in FIGS. 1A-1C.

Unlike conventional processing techniques, the illustrated method offabrication provides for a substantially gapless color filter arraywithout a high incidence of problems associated with the shifting offocal points of overlying microlenses. The reduction of the shiftingfocal lengths problem improves the overall quantum efficiency.Additionally, the first and second material layers can be deposited ontoasymmetrically formed photosensitive regions, as discussed below withrespect to FIGS. 8-10B.

It should also be noted that although the conforming layers 182 _(B),182 _(G), 182 _(R) are illustrated as filtering a correspondingwavelength of light from striking the photosensitive regions 104 _(B),104 _(G), 104 _(R), the embodiment of the invention is not so limited.For example, the conforming layers 182 _(B), 182 _(G), 182 _(R) couldall be formed of the same material, and the filtering of correspondingwavelengths of light could be performed by the underlying base materiallayers 181 _(B), 181 _(G), 181 _(R). The base material layers 181 _(B),181 _(G), 181 _(R) are patterned in successive patterning steps suchthat first, second, and third wavelengths of light are filtered by thebase material layers 181 _(B), 181 _(G), 181 _(R), and strike theintended photosensitive regions 104 _(B), 104 _(G), 104 _(R).

Although FIGS. 2A-2D are illustrated as having the conforming layers 182_(B), 182 _(G), 182 _(R) formed between the base material layers 181_(B), 181 _(G), 181 _(R), it should be recognized that the conforminglayers 182 _(B), 182 _(G), 182 _(R) could be between and over the basematerial layers 181 _(B), 181 _(G), 181 _(R), as illustrated below withrespect to FIG. 4.

Additional material layers could be formed over the FIG. 1A imagerdevice 100. For example, as illustrated in FIG. 3, a coating 110′ couldbe formed over the FIG. 1A imager device 100 to arrive at the FIG. 3imager device 100′. The coating 110′ is illustrated as beingsubstantially planar, which may provide for better handling throughoutsubsequent manufacturing processes and additional rigidity to theoverall imager device 100′. The substantially planar coating 110′ couldbe formed by conventional coating methods, including, but not limitedto, spin-coating methods, as discussed above. The coating 110′ could beformed of any of the materials discussed above with respect to FIG. 2A.

FIG. 4 illustrates a cross-sectional view of an imager device 200constructed in accordance with a third embodiment of the invention. Likethe imager device 100 illustrated in FIGS. 1A-1C, the FIG. 4 imagerdevice 200 has an array of first, second, and third pixel cells 202,202′, 202, respectively. At least one of the pixel cells (i.e., pixelcell 202′) is different from the other two pixel cells (i.e., pixelcells 202) in the array. As discussed above with respect to FIGS. 2A-2D,the materials forming the conforming layers 208 b, 208 b′, 208 b areselected (based on their respective surface tensions) or deposited inconditions such that they form rounded structures over the underlyingbase material layers 208 a, 208 a′, 208 a.

The illustrated imager device 200 has a second pixel cell 202′ having adifferent radius of curvature R′ from the radius of curvatures R of theadjacent first and third pixel cells 202. In the embodiment, the firstand third pixel cells 202 correspond to a first wavelength of light, andthe second pixel cell 202′ corresponds to a second wavelength of light,which is different from the first wavelength of light.

FIG. 4 illustrates the second pixel cell 202′ having a color filter 208′that has a base material layer 208 a′ formed below a conforming layer208 b′. The first and third pixel cells 202 also have color filters 208comprised of base material layers 208 a formed below conforming layers208 b.

The base material layer 208 a′ has a height h′ that is different fromthe heights h associated with adjacent base material layers 208 a suchthat the conforming layer 208 b′ comprises a different volume whencompared to the adjacent conforming layers 208 b. The smaller volume ofthe conforming layer 208 b′ reduces the overall radius of curvature R′of the color filter 208′ as compared to adjacent color filters 208. Byvarying the underlying size (one or more of height, weight, length) ofbase material layers (e.g., base material layers 208 a, 208 a′), thevolume of the overlying conforming layer (e.g., conforming layer 208 b,208 b′) can be varied. By varying the volume of the conforming layer 208b, 208 b′, the overall radius of curvatures (e.g., radius of curvaturesR, R′) can also be varied, which may result in varied (or asymmetrical)focal lengths 122, 122′.

The ability to vary the focal lengths (e.g., focal lengths 122, 122′) ofthe overall color filters 208, and, to an extent necessary, the focallengths of optional overlying coating 210, 210′, is important in imagecapture. As is known in the art, light at different wavelengths isabsorbed at different depths within a photosensitive region; wavelengthscorresponding to blue are typically absorbed near the top surfaces ofphotosensitive regions (e.g., photosensitive region 204), wavelengthscorresponding to red are typically absorbed at or near the p-n junctionsof photosensitive regions, and wavelengths corresponding to green aretypically absorbed between the top surfaces and p-n junctions ofphotosensitive regions.

FIG. 4 illustrates pixel cells 202, 202′ that have focal lengths 122,122′ that are optimized for the absorption of wavelengths correspondingto the colors red and green, respectively. The imager device 200 hascolor filters 208, 208′ that have radius of curvatures R, R′,respectively, that are designed to focus light onto respectivephotosensitive regions 204, 204′.

The FIG. 4 imager device 200 is fabricated in substantially the samemanner as the imager device 100 illustrated in FIGS. 1A and 1B; at leastone of the base material layers (e.g., base material layer 208 a′) istypically planarized to a lower height h′ than adjacent base materiallayers (e.g., first material layers 208 a) having a greater height h.The second material layers 208 b, 208 b′ are subsequently formed overthe base material layers 208 a, 208 a′ to form the overall color filter208. The optional coating 210, 210′ can be formed over the color filters208, 208′, if desired.

FIGS. 5A and 5B illustrate top-down and cross-sectional view,respectively, of an imager device 300 constructed in accordance with afourth embodiment of the invention. FIG. 5A illustrates a Bayer patterncomprising first, second, and third pixel cells 302 a, 302 b, 302 c. Asillustrated in FIG. 5B, a cross-sectional view taken along line III-IIIof FIG. 5A, the first pixel cell 302 a has a first color filter 308 ahaving a first base material layer 308 aa formed below a firstconforming layer 308 ba. An optional first coating 310 a is illustratedas being formed over the first color filter 308 a. The first basematerial layer 302 aa of the first color filter 308 a has a height ha,which results in the first color filter 308 a and the overlying firstcoating 310 a having a first radius of curvature Ra. The first radius ofcurvature Ra is illustrated as being shorter in comparison to adjacentsecond and third radius of curvatures Rb, Rc, respectively. The firstradius of curvature Ra directs light onto a first focal plane 322 a. Thefirst focal length coincides with the absorption depth of wavelengths oflight corresponding to the color blue in a first photosensitive region304 b, as discussed above with respect to FIG. 4.

The second pixel cell 302 b has a second color filter 308 b having asecond base material layer 308 ab formed below a second conforming layer308 bb. An optional second coating 310 b is formed over the second colorfilter 308 b of the imaging device 300. The illustrated second basematerial layer 308 ab has a second height hb, which effects theoverlying curvature of the second color filter 308 b and the secondcoating 310 b resulting in a second radius of curvature Rb. The radiusof curvature Rb is such that the second color filter 308 b and thesecond coating 310 b direct light onto a second focal length 322 b; thesecond focal length 322 b coincides with the absorption depth ofwavelengths of light corresponding to the color green in a secondphotosensitive region 304 g, as discussed above with respect to FIG. 4.

Similarly, the third pixel cell 302 c has a third color filter 308 chaving a third base material layer 308 ac formed below a thirdconforming layer 308 bc. An optional third coating 310 c is formed overthe third color filter 308 c of the imaging device 300. The illustratedthird base material layer 308 ac has a third height hc, which effectsthe overlying curvature of the third color filter 308 c and the thirdcoating 310 c resulting in a third radius of curvature Rc. The radius ofcurvature Rc is such that the third color filter 308 c and the thirdcoating 310 c direct light onto a third focal length 322 c; the thirdfocal length 322 c coincides with the absorption depth of wavelengths oflight corresponding to the color red in a third photosensitive region304 r, as discussed above with respect to FIG. 4.

The imager device 300 of FIGS. 5A and 5B is fabricated in substantiallythe same manner as the imager device 100 of FIGS. 1A and 1B (illustratedin FIGS. 2A-2E); however, the first base material layer 308 aa is formedprior to the second and third base material layers such that the firstbase material layer 308 aa can be planarized to a height ha prior to thedeposition of the second and third base material layers 308 ab, 308 ac.Similarly, the second base material layer 308 ab is formed prior to thethird base material layer 308 ac, such that the second base materiallayer 308 ab can be planarized to a height hb prior to the deposition ofthe third base material layer 308 ac. The first, second, and thirdconforming layers 308 ba, 308 bb, 308 bc are subsequently formed overrespective first, second, and third base material layers 308 aa, 308 ab,308 ac to form the overall first, second, and third color filters 308 a,308 b, 308 c. The optional coating 310 a, 310 b, 310 c can be formedover the color filters 308 a, 308 b, 308 c, if desired.

FIG. 6 illustrates an imager device 300′ constructed in accordance witha fifth embodiment of the invention. The illustrated cross-sectionalview of the imager device 300′ is taken along line III-III of FIG. 5A.The imager device 300′ is similar to the FIG. 5 imager device 300;however, the imager device 300′ has first, second, and third basematerial layers 308 aa′, 308 ab′, 308 ac′ comprised of multiple materiallayers (or stacks). The first, second, and third base material layers308 aa′, 308 ab′, 308 ac′ are formed by depositing multiple materiallayers over the passivation layer 120. The multiple material layers maybe deposited by any deposition technique; for example, spin-coatdeposition. The multiple layers are subsequently selectively etched andselectively planarized to form first, second, and third base materiallayers 308 aa′, 308 ab′, 308 ac′ having different heights ha, hb, hc,respectively. The first, second, and third conforming layers 308 ba, 308bb, 308 bc are formed over the first, second, and third base materiallayers 308 aa′, 308 ab′, 308 ac′ resulting in first, second, and thirdcolor filters 308 a, 308 b, 308 c with first, second, and third radiusof curvatures Ra, Rb, Rc, respectively.

FIG. 7 illustrates further optional processing of the FIG. 5 imagerdevice 300. Specifically the first, second, and third color filters 308a, 308 b, 308 c and the first, second, and third coating 310 a, 310 b,310 c are selectively etched to create vias 360 in between the first,second, and third pixel cells 302 a, 302 b, 302 c. Creating vias 360 mayreduce the amount of cross-talk between pixel cells (e.g., first,second, and third pixel cells 302 a, 302 b, 302 c). “Cross-talk” resultswhen off-axis wavelengths of light strike a coating or color filter atan obtuse angle of incidence. The off-axis wavelengths of light passthrough material layers and miss the intended photosensitive regions,and instead strike adjacent photosensitive regions. Creating the vias360 isolate the first, second, and third pixel cells 302 a, 302 b, 302 cfrom one another such that the incidence of cross-talk may decrease.

FIG. 8 illustrates further optional processing of the FIG. 7 imagerdevice 300. To further reduce the incidence of cross-talk, spacerstructures 362 made of an opaque material may be formed within the vias360 (FIG. 6). The spacer structures 362 can be formed by conventionaldeposition techniques. The spacer structure 362 limit wavelengths oflight from striking the first, second, and third photosensitive regions304 b, 304 g. 304 r of the first second and third pixel cells 302 a, 302b, 302 c.

It should be noted that the FIG. 5 imager device need not be furtherprocessed, and that the illustrations and descriptions relating to FIGS.7-8 are only optional. Additionally, it should be noted that the imagerdevice 300 of FIGS. 5-8 may undergo further processing, and that theillustrations and descriptions thereto are only examples.

FIGS. 9A and 9B illustrate top-down and cross-sectional views,respectively, of an imager device 400 constructed in accordance with aneighth embodiment of the invention. FIG. 9A illustrates a Bayer patterncomprising first, second, and third pixel cells 402 a, 402 b, 402 c. Asillustrated in FIG. 9B, a cross-sectional view taken along line IV-IV ofFIG. 9A, The imager device 400 is similar to the FIG. 8 imager device300; however, the processing steps performed to form the FIG. 9 imagerdevice 400 are different, resulting in structural differences betweenthe two imager devices.

As illustrated, the imager device 400 has first, second and third pixelcells 402 a, 402 b, 402 c having respective first second and third colorfilters 408 a, 408 b, 408 c. The first second and third color filters408 a, 408 b, 408 c have respective first, second, and third basematerial stacks 481 a, 481 b, 481 c, formed below respective first,second, and third conforming layers 482 a, 482 b, 482 c. The illustratedfirst, second and third base material stacks 481 a, 482 b, 482 c areformed of multiple material layers in substantially the same manner asdiscussed above with respect to FIG. 6. Spacer structures 462 aresubsequently formed between the first, second, and third base materialstacks 481 a, 482 b, 482 c. The first, second, and third conforminglayers 482 a, 482 b, 482 c are deposited over respective first, second,and third base material stacks 481 a, 482 b, 482 c, and take on a shapebased on the heights of the first, second, and third base materialstacks 481 a, 482 b, 482 c. The interaction between the material used toform the first, second, and third conforming layers 482 a, 482 b, 482 cand the spacer structures 462 results in the first, second, and thirdconforming layers 482 a, 482 b, 482 c having corresponding first,second, and third shapes.

As illustrated, the first conforming layer 482 a has a depressed shapeas a result of the first base material stack 481 a having a topmostsurface with a height less than a topmost surface of the adjacent spacerstructures 462. Due to the surface tension of the material used to formthe first conforming layer 482 a, the resulting first conforming layer482 a has edges 483 a that have topmost surfaces with a height h1greater than the height h2 of a middle portion 484 a of the firstconforming layer 482 a. The first color filter 408 a directs light ontoa focal plane 422 a at or near to a top surface of a respectivephotosensitive region 404 b. Although illustrated as having edges 483 athat have topmost surfaces with a height h1 greater than the height h2of a middle portion 484 a of the first conforming layer 482 a, this isnot intended to be limiting in any way.

For example, the second pixel cell 402 b includes the second colorfilter 408 b having a second base material stack 481 b that issubstantially the same height h3 as the adjacent spacer structures 462.Edges 483 b of the overlying second conforming layer 482 b, therefore,have a height h4 lower than a height h5 associated with a middle portion484 b of the second conforming layer 482 b. As a result of the surfacetension inherent in the material used to form the second conforminglayer 482 b, the middle portion 484 b of the second conforming layer 482b is substantially planar. The second color filter 408 b directs lightonto a focal plane 422 b corresponding to a depth below a top surface ofa respective photosensitive region 404 g.

The third pixel cell 402 c includes the third color filter 408 c havinga third base material stack 481 c with a height greater than theadjacent spacer structures 462. As a result of the surface tensioninherent in the material used to form the third conforming layer 482 c,a middle portion 484 b of the second conforming layer 482 c has asubstantially hemi-spherical shape. The third color filter 408 c directslight onto a focal plane 422 c corresponding to a depth near the p-njunction of a respective photosensitive region 404 c.

It should be noted that the heights of the base material stack andspacer structures could be selected such that the conforming layers aresubstantially planar after deposition. The substantially planar surfacewould allow for an ideal platform on which microlenses could besubsequently formed. Additionally, the heights of the base materialstack and spacer structures could be selected such that the conforminglayers are substantially non-planar after deposition. By controlling theshapes of the underlying color filter, the focal points of depositedmicrolenses could be controlled to have shifted focal points relative toa center of the microlens.

FIGS. 10A and 10B illustrate top-down and cross-sectional views,respectively, of an imager device 500 constructed in accordance with aninth embodiment of the invention. FIG. 10A illustrates a Bayer patterncomprising first, second, and third pixel cells 502 a, 502 b, 502 c. Asillustrated in FIG. 10B, a cross-sectional view taken along line V-V ofFIG. 10A, the imager device 500 includes first, second, and third pixelcells 502 a, 502 b, 502 c having respective first, second, and thirdcolor filters photosensitive regions 504 b, 504 g, 5404 r. The first andsecond photosensitive regions 504 b, 504 g have a first distance D1between each other; the second and third photosensitive regions 504 g,5404 r have a second distance D2 between each other. As illustrated, thefirst distance D1 is greater than the second distance D2. Shared pixelcell technologies typically employ asymmetrical distances betweenphotosensitive regions of a pixel array.

Accordingly, the first second and third color filters 508 a, 508 b, 508c have respective first, second, and third base material layers 581 a,581 b, 581 c, formed below respective first, second, and thirdconforming layers 582 a, 582 b, 582 c. The first, second, and third basematerial layers 581 a, 581 b, 581 c are patterned over the first,second, and third photosensitive regions 504 a, 504 b, 504 c. The firstbase material layer 581 a has a first height h and a first width w. Thesecond and third base material layers 581 b, 581 c have a second heighth′ that is less than the first height h and a second width w′ that isless than the first width w.

The lower height h′ and the smaller width w′ of the second and thirdbase material layers 581 b, 581 c, results in a smaller overall radiusof curvature R′ of the second and third color filters 508 b, 508 c ascompared to the overall radius of curvature R associated with the firstcolor filter 508 a. The second and third color filters 508 b, 508 c aretailored for the underlying second and third photosensitive regions 504b, 504 c. Additionally, the smaller width w′ of the second and thirdbase material layers 581 b, 581 c allow the second and third colorfilters 508 b, 508 c to be formed in proximity to one another. Asillustrated the second and third color filters 508 b, 508 c have a thirddistance D3 from one another, corresponding to the second distance D2between the respective photosensitive regions 504 g, 5404 r. The firstand second color filters 508 a, 508 b have a fourth distance D4 from oneanother, corresponding to the first distance D1 of the underlyingrespective photosensitive regions 504 b, 504 c.

It should also be noted that although FIGS. 1-10B illustrate three pixelcells, it is not intended to be limiting in any way. Those skilled inthe art will recognize that a plurality of pixel cells is typicallyfabricated in rows and columns in an array on a single substratesimultaneously. Moreover, as noted the embodiments of the invention arenot limited to a pixel array employs there color pixels.

FIG. 11 illustrates a device 608 incorporating an imager 100 constructedin accordance with the embodiments of the invention. For the sake ofclarity, the imaging device will be described as including the FIG. 1imager device 100 of FIGS. 1A and 1B; however, it should be noted thatany of the embodiments described with respect to FIGS. 1A-10B could beemployed for the array of imager device 100.

In operation of the FIG. 11 device 608, the pixel cells 102 of each rowin the imager device 100 are all turned on at the same time by a rowselect line, and the pixel cells 102 of each column are selectivelyoutput by respective column select lines. A plurality of row and columnlines is provided for the entire array of pixel cells. The row lines areselectively activated in sequence by the row driver 610 in response torow address decoder 620 and the column select lines are selectivelyactivated for each row by the column driver 660 in response to columnaddress decoder 670. Thus, a row and column address is provided for eachpixel cell 102. The device 608 is operated by the control circuit 650,which controls address decoders 620, 670 for selecting the appropriaterow and column lines for pixel readout, and row and column drivercircuitry 610, 660, which apply driving voltage to the drive transistorsof the selected row and column lines.

The pixel output signals typically include a pixel reset signal V_(rst)taken off of a floating diffusion region (via a source followertransistor) when it is reset and a pixel image signal V_(sig), which istaken off the floating diffusion region (via the source followertransistor) after charges generated at a photosensor by an image aretransferred to it. The V_(rst) and V_(sig) signals are read by a sampleand hold circuit 661 and are subtracted by a differential amplifier 662,which produces a difference signal (V_(rst)−V_(sig)) for each pixel cell102, which represents the amount of light impinging on the pixel cell102. This signal difference is digitized by an analog-to-digitalconverter (ADC) 675. The digitized pixel signals are then fed to animage processor 680 to form a digital image output. In addition, asdepicted in FIG. 10, the imaging device 608 may be included on a singlesemiconductor chip (e.g., chip substrate 600).

Detailed descriptions of the functions of various CMOS elements of animaging circuit are described, for example, in U.S. Pat. No. 6,140,630;U.S. Pat. No. 6,376,868; U.S. Pat. No. 6,310,366; U.S. Pat. No.6,326,652; U.S. Pat. No. 6,204,524; U.S. Pat. No. 6,333,205; and U.S.Pat. No. 6,852,591, all of which are assigned to Micron Technology, Inc.The disclosures of each of the foregoing are hereby incorporated byreference in their entirety.

FIG. 12 shows a system 900, a typical processor system modified toinclude an imaging device (such as the FIG. 11 device 608) of theembodiments of the invention. The processor system 900 is an example ofa system having digital circuits that could include image sensordevices. Without being limiting, such a system could include a computersystem, camera system, scanner, machine vision, vehicle navigation,video phone, surveillance system, auto focus system, star trackersystem, motion detection system, image stabilization system, and othersystems employing an imager.

System 900, for example a digital camera system, generally comprises acentral processing unit (CPU) 902, such as a microprocessor whichperforms camera control and may also perform image providing functions,that communicates with an input/output (I/O) device 906 over a bus 904.Device 608 also communicates with the CPU 902 over the bus 904. Theprocessor-based system 900 also includes random access memory (RAM) 910,and can include removable memory 914, such as flash memory, which alsocommunicate with the CPU 902 over the bus 904. The device 608 may becombined on a same chip as the CPU 902, with or without memory storage,or on a different chip from the CPU 902.

It should again be noted that although the embodiments of the inventionhave been described with specific references to CMOS imaging devices(e.g., 100, 200, 300, 400, 500 of FIGS. 1A-10B), they have broaderapplicability and may be used in any imaging apparatus. For example,embodiments may be used in conjunction with charge coupled device (CCD)imagers. The above description and drawings illustrate embodiments whichachieve the objects and features of the invention. Although certainadvantages and embodiments have been described above, those skilled inthe art will recognize that substitutions, additions, deletions,modifications and/or other changes may be made. Accordingly, theembodiments are not limited by the foregoing description but are onlylimited by the scope of the appended claims.

1. A pixel cell, comprising: a photosensitive region formed inassociation with a substrate; and a color filter formed over thephotosensitive region, the color filter comprising: a first materiallayer; and a second material layer formed over the first material layerhaving a shape defined at least in part by the first material layer. 2.The pixel cell of claim 1, wherein at least one of the first and secondmaterials has color filtering properties.
 3. The pixel cell of claim 1,wherein the first material layer further comprises a plurality ofmaterial blocks.
 4. The pixel cell of claim 1, wherein the secondmaterial layer is formed over a surface of the first material layer. 5.The pixel cell of claim 1, wherein the first material layer has a firstrefractive index, and the second material layer has a second refractiveindex different from the first refractive index.
 6. The pixel cell ofclaim 1, wherein the second material layer forms a microlens for thepixel cell.
 7. The pixel cell of claim 6, wherein a coating is formed ona surface of the second material layer.
 8. The pixel cell of claim 7,wherein the second material layer has a curved shape with a first radiusof curvature, and the coating has a shape configuring to that of thesecond material and a second radius of curvature of the second materiallayer different from the first radius of curvature.
 9. The pixel cell ofclaim 7, wherein the coating has a substantially planar upper surface.10. The pixel cell of claim 1, wherein the photosensitive region isselected from the group consisting of a photodiode, a photogate and aphotosensor.
 11. The pixel cell of claim 1, wherein one of the first andsecond material layers are formed of a material selected from the groupconsisting of zinc selenide (ZnSe), silicon oxide, silicon nitride,silicon oxynitride, silicon-carbon (SiC) (BLOk), tantalum pentoxide(Ta₂O₅), titanium oxide (TiO₂), polymethylmethacrylate, polycarbonate,polyolefin, cellulose acetate butyrate, polystyrene, polyimide, epoxyresin, photosensitive gelatin, acrylate, methacrylate, urethaneacrylate, epoxy acrylate, polyester acrylate, a positive photoresist,and a negative photoresist.
 12. The pixel cell of claim 11, wherein atleast one of the first and second material layers is formed of aphotoresist fabricated by FUJIFILM Electronic Materials.
 13. The pixelcell of claim 12, wherein at least one of the first and second materiallayers is formed from a material selected from the group consisting ofSB-3000L, SG-3000L and SR-3000L.
 14. The pixel cell of claim 1, whereinthe first material layer is formed as a plurality of material layers.15. The pixel cell of claim 1, wherein the second material layer isseparated by spaces from adjacent second material layers.
 16. The pixelcell of claim 1, wherein the first material layer is separated by spacesfrom adjacent first material layers, and wherein the second materiallayers have a shape defined at least in part by the first materiallayers.
 17. An imager, comprising: a pixel cell array formed in asubstrate, the pixel cell array having an array of at least first,second, and third photosensors; and a color filter array comprising atleast first, second, and third color filters corresponding to the first,second, and third photosensors, and comprising respective first, second,and third shaped layers formed over respective first, second, and thirdbase layers.
 18. The imager of claim 17, further comprising a coatingformed over the color filter array.
 19. The imager of claim 17, whereinthe first, second and third base layers comprise spaced blocks of basematerial.
 20. The imager of claim 19, wherein the first, second, andthird base blocks have respective first, second, and thirdcross-sectional widths.
 21. The imager of claim 20, wherein the first,second, and third color filters have respective first, second, and thirdradius of curvatures.
 22. The imager of claim 21, wherein at least twoof the first, second, and third radius of curvatures are different fromeach other.
 23. The imager of claim 17, wherein the coating comprises atleast first, second, and third coating layers formed respectively oversurfaces of the first, second, and third color filters.
 24. The imagerof claim 23, wherein the first, second, and third coating layers haverespective first, second, and third radius of curvatures, at least twoof the radius of curvature being different from each other.
 25. Theimager of claim 17, further comprising spacer structures spaced betweeneach of the first, second and third blocks of base layers.
 26. Theimager of claim 17, wherein the shaped layers formed over the baselayers have a shape defined at least in part by the base layer.
 27. Theimager of claim 17, wherein at least one of the base layers furthercomprises a plurality of material blocks.
 28. The imager of claim 17,wherein the shaped layers formed over the base layers have a shapedefined at least in part by the base layers and spaces formed betweenthe base layers.
 29. The imager of claim 28, wherein at least two of theshaped layers have different shapes from one another.
 30. The imager ofclaim 17, wherein at least two of the first, second and third colorfilters have different focal lengths.
 31. The imager of claim 17,wherein the shaped layers form a microlens for respective pixel cells32. The imager of claim 17, wherein the base layers are spaced apartfrom one another, and at least two of the base layers are closer inproximity than one of the at least two base layers and a third baselayer.
 33. An imager, comprising: a pixel cell array formed in asubstrate, the pixel cell array having an array of photosensors; and acolor filter array corresponding to the array of photosensors, andcomprising respective shaped layers formed over respective base layers,wherein at least one of the base layers has physical dimensionsdifferent from at least another of the base layers.
 34. The imager ofclaim 33, wherein the different physical dimension is height.
 35. Theimager of claim 33, wherein the different physical dimension is width.36. The imager of claim 33, wherein a shaped layer formed over thedifferent base layer has a shape defined at least in part by thedifferent base layer.
 37. The imager of claim 33, wherein a shaped layerformed over the different base layer has a shape defined at least inpart by the different base layer and spacing structures formed betweenadjacent base layers.
 38. A method of forming an imaging device,comprising: forming a pixel cell array in a substrate, the pixel cellarray having an array of photosensors; forming a color filter arraycorresponding to the array of photosensors, each of the color filterscomprising respective conforming layers formed over base layers; andforming a coating formed over the color filter array.
 39. The methodaccording to claim 38, wherein the color filter array is formed bydepositing a base layer precursor on a substantially planar materiallayer by spin coat deposition, and patterning vias within the base layerprecursor to form an array of base layers.
 40. The method of claim 39,wherein the conforming layers are deposited over the array of baselayers by spin coat deposition.
 41. The method of claim 40, wherein theconforming layers have a shape defined at least partially by the baselayers.
 42. The method of claim 38, further comprising forming spacerstructures between at least two of the base layers.
 43. The method ofclaim 42, wherein the conforming layers have a shape defined at leastpartially by the base layers and the spacer structures.
 44. The methodof claim 38, wherein the base layers comprise a plurality of materiallayers deposited by spin coat deposition.
 45. The method of claim 44,wherein at least one of the base layers is selectively planarized suchthat at least two of the base layers have different cross-sectionalheights.
 46. The method of claim 44, wherein at least one of the baselayers is selectively etched such that at least two of the base layershave different cross-sectional widths.
 47. A processor system,comprising: a processor; and an imager coupled to the processor, theimager comprising; a pixel cell array formed in a substrate, the pixelcell array having an array of at least first, second, and thirdphotosensors; a color filter array comprising at least first, second,and third color filters corresponding to the first, second, and thirdphotosensors, each of the first, second, and third color filterscomprising respective first, second, and third conforming layers formedover first, second, and third base structures; and a microlens arrayformed over the color filter array.
 48. The processor system of claim47, wherein a distance between the first and second color filters isgreater than a distance between the second and third color filters. 49.The processor system of claim 47, wherein the first, second, and thirdbase structures have respective first, second, and third heights, andwherein the first, second, and third heights are different from oneanother.
 50. The processor system of claim 49, wherein the first,second, and third color filters have respective first, second, and thirdcolor filters have first, second, and third radius of curvatures, andwherein the first, second, and third radius of curvatures are differentfrom one another.
 51. The processor system of claim 50, wherein thefirst, second, and third radius of curvatures have corresponding first,second, and third focal lengths, each corresponding to a different depthof respective photosensors.
 52. The processor system of claim 47,wherein at least one of the color filters has a conforming layer havinga middle portion lower than an edge of the conforming layer.
 53. Theprocessor system of claim 47, wherein the processing system is a digitalcamera system.
 54. The processor system of claim 53, wherein theprocessing system is a video camera system.
 55. The processor system ofclaim 53, wherein the processing system is a still camera system.
 56. Apixel cell array, comprising: a plurality of photosensitive regionsformed in association with a substrate; and a color filter array formedover the plurality of photosensitive regions, at least one color filtercomprising: a first material layer; and a second material layer formedbetween the first base material layer and an adjacent color filter. 57.The pixel cell array of claim 56, wherein the base material layerfurther comprises a plurality of material blocks.
 58. The pixel cellarray of claim 56, wherein the second material layer is formed over asurface of the first material layer.
 59. The pixel cell array of claim56, wherein one of the first and second material layers are formed of amaterial selected from the group consisting of zinc selenide (ZnSe),silicon oxide, silicon nitride, silicon oxynitride, silicon-carbon (SiC)(BLOk), tantalum pentoxide (Ta₂O₅), titanium oxide (TiO₂),polymethylmethacrylate, polycarbonate, polyolefin, cellulose acetatebutyrate, polystyrene, polyimide, epoxy resin, photosensitive gelatin,acrylate, methacrylate, urethane acrylate, epoxy acrylate, polyesteracrylate, a positive photoresist, and a negative photoresist.
 60. Thepixel cell array of claim 56, wherein a coating is formed on a surfaceof the second material layer.